#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>

int main()
{
	long double num=1.0;
	long double temp;
	long double sum1 = 0.0;
	long double sum2 = 0.0;
	for (int i = 1; i <= 100; i+=2)
	{
		temp = num / i;
		sum1 = sum1 + temp;
	}
	for (int i = 0 ; i <= 100; i += 2)
	{
		if (i == 0)
		{
			continue;
		}
		temp = num / i;
		sum2 = sum2 + temp;
	}
	printf("%llf ", sum1-sum2);
	return 0;
}